Cold pressed polyester adhesive electrical laminated paperboard

Abstract

The present invention provides a cold-pressed polyester adhesive electrical laminated paperboard, comprising a plurality of stacked insulating paperboards and a plurality of polyester adhesive layers, wherein a layer of the polyester adhesive layer is arranged between each two adjacent insulating paperboards, wherein each of the polyester adhesive layers is used to bond two adjacent insulating paperboards together through a cold-pressing process, wherein the polyester adhesive layer comprises an adhesive layer, a first permeable structure and a second permeable structure, wherein the adhesive layer is formed between two adjacent insulating paperboards, wherein the first permeable structure extends from one side of the adhesive layer to the insulating paperboard on the side and permeates into the insulating paperboard on the side by a first thickness, wherein the second permeable structure extends from the other side of the adhesive layer to the insulating paperboard on the other side and permeates into the insulating paperboard on the other side by a second thickness.

Description

Technical Field

[0001] The present invention relates to the field of laminated paperboard, and more particularly to a cold-pressed polyester adhesive laminated paperboard for electrical use. Background Art

[0002] Insulating paperboard is a commonly used paperboard in the transformer field. As an important insulating paperboard, laminated paperboard can be further processed and used as insulating end rings for transformers. The function of the insulating end rings for transformers is mainly to fix and insulate the transformer windings to ensure the normal operation of the transformer. Specifically, the insulating end rings can withstand the electric field, magnetic field and continuous load during the operation of the transformer, and transfer them to the supporting structure of the winding. At the same time, the insulating end rings can enhance the insulation performance of the windings and prevent current and other external factors from damaging the windings. In addition, the material and manufacturing process of the insulating end rings also need to meet specific requirements. For example, it needs to have good electrical properties, heat resistance and mechanical strength to ensure stable performance during the long-term operation of the transformer. Therefore, the role of the transformer insulating end ring is crucial, which can ensure the safe and stable operation of the transformer, thereby ensuring the normal operation of the power system.

[0003] At present, phenolic resin is commonly used as the adhesive for insulating paperboard laminates for oil-immersed transformers and reactors in China. Phenolic resin is a polar molecular polymer that forms a cross-linked network structure after curing. The thermal stability of phenolic resin can reach 300°C, but under long-term working conditions above 120°C, small cracks will appear inside the resin, thereby reducing its electrical and mechanical properties. At the same time, when phenolic resin is directly applied on the insulating paperboard, it is difficult to control the thickness of the brushing. When more resin is applied, closed bubbles are easily generated during hot pressing, resulting in partial discharge. Therefore, liquid phenolic resin is generally only suitable for bonding laminated products used on distribution transformers.

[0004] In order to solve the problem of uneven brushing of liquid phenolic resin, some insulation material manufacturers have developed phenolic resin sizing paper made of cellulose paper as the base material and coated with phenolic resin, also known as double-sided sizing paper. Because it is very easy to absorb moisture, the resin will accelerate self-curing at higher temperatures. Therefore, the sizing paper has certain temperature, humidity and storage time requirements for storage. Since the softening point of phenolic resin is 85-100℃ and its curing temperature is 170-175℃, the moisture in the cardboard and the volatile matter in the sizing paper will evaporate above 85℃, and the evaporation rate will be faster as the temperature increases. If the ingredients and pressing process are improper, and the air permeability of the sizing paper is extremely poor, it is easy to produce irregular tiny air gaps at the interface between the sizing paper and the insulating cardboard. Therefore, when using phenolic sizing paper as an adhesive for laminated cardboard, the partial discharge value will also be high. At the same time, the glue content and soluble volatiles in the sizing paper have a great influence on the mechanical, electrical and interlayer bonding of the laminated insulating cardboard.

[0005] When phenolic, epoxy, polyvinyl acetate emulsion, polyvinyl acetal, polyvinyl alcohol, etc. are used as adhesives for insulating paperboards, they all need to be diluted with organic solvents. There will be a certain amount of volatile matter in this type of adhesive, and it is difficult to avoid the generation of irregular air gaps during pressing and bonding, causing the insulating parts to occasionally have excessive partial discharge.

[0006] In order to adapt to the development of power transformers towards high voltage and large capacity, especially the manufacture of converter transformers, foreign power insulation material manufacturers have developed a new type of electrical insulation paperboard adhesive with high mechanical strength and excellent electrical properties. After the successful development of power insulation materials, manufacturers did not disclose the relevant technology or provide corresponding adhesives, but only sold finished transformer insulation end rings or standard-sized laminates to companies in need. Summary of the invention

[0007] One object of the present invention is to provide a cold-pressed polyester adhesive laminated paperboard for electrical use, wherein polyester adhesive is pressed onto insulating paperboard by cold pressing, thereby obtaining the cold-pressed polyester adhesive laminated paperboard for electrical use.

[0008] Another object of the present invention is to provide a cold-pressed polyester adhesive electrical laminated paperboard, wherein during the production process of the cold-pressed polyester adhesive electrical laminated paperboard, a press is used to press the polyester adhesive onto the insulating paperboard, and the entire process does not require heating, thereby achieving room temperature curing of the electrical laminated paperboard adhesive.

[0009] Another object of the present invention is to provide a cold-pressed polyester adhesive electrical laminated paperboard, wherein compared with existing laminated paperboards, the cold-pressed polyester adhesive electrical laminated paperboard has higher mechanical strength and better electrical performance.

[0010] Another object of the present invention is to provide a cold-pressed polyester adhesive laminated paperboard for electrical use, wherein the cold-pressed polyester adhesive laminated paperboard for electrical use has high mechanical strength, thereby effectively reducing the requirements for the thickness of the laminated board in practical applications, thereby requiring less raw materials for the insulation board, and being more economical and environmentally friendly.

[0011] Another object of the present invention is to provide a cold-pressed polyester adhesive laminated paperboard for electrical use, wherein the cold-pressed polyester adhesive laminated paperboard for electrical use has high mechanical strength, so that the preset mechanical strength requirement can be achieved with a thinner thickness, so that the insulating end ring for the transformer made of the cold-pressed polyester adhesive laminated paperboard for electrical use can be designed to be thinner, and then the required core column height can be set to be lower, and then the use of silicon steel sheets is reduced.

[0012] Another object of the present invention is to provide a cold-pressed polyester adhesive laminated paperboard for electrical use, wherein the cold-pressed polyester adhesive laminated paperboard for electrical use has high mechanical strength, so that the preset mechanical strength requirement can be achieved with a thinner thickness, so that the insulating end ring for the transformer made of the cold-pressed polyester adhesive laminated paperboard for electrical use can be designed to be thinner, and thus the overall size is smaller, thereby reducing the use of insulating oil.

[0013] Another object of the present invention is to provide a cold-pressed polyester adhesive laminated paperboard for electrical use, wherein the cold-pressed polyester adhesive laminated paperboard for electrical use has high mechanical strength, so that the preset mechanical strength requirement can be achieved with a thinner thickness, so that the cold-pressed polyester adhesive laminated paperboard for electrical use used as an insulating end ring for a transformer can be designed to be thinner, thereby reducing the use of fuel tank steel plates.

[0014] Another object of the present invention is to provide a cold-pressed polyester adhesive laminated paperboard for electrical use, wherein the cold-pressed polyester adhesive laminated paperboard for electrical use has high mechanical strength, so that the preset mechanical strength requirement can be achieved with a thinner thickness, so that the insulating end ring for transformers made with the cold-pressed polyester adhesive laminated paperboard for electrical use can be designed to be thinner, thereby reducing the usage of silicon steel sheets, insulating oil and oil tank steel plates, thereby improving the performance of the insulating end ring for transformers while reducing the cost of the insulating end ring for transformers.

[0015] Another object of the present invention is to provide a cold-pressed polyester adhesive laminated paperboard for electrical use, wherein the polyester adhesive used in the cold-pressed polyester adhesive laminated paperboard for electrical use has excellent electrical properties and insulation properties.

[0016] Another object of the present invention is to provide a cold-pressed polyester adhesive laminated paperboard for electrical use, wherein the polyester adhesive used in the cold-pressed polyester adhesive laminated paperboard for electrical use does not pollute transformer oil.

[0017] Another object of the present invention is to provide a cold-pressed polyester adhesive laminated paperboard for electrical use, wherein the polyester adhesive used in the cold-pressed polyester adhesive laminated paperboard for electrical use has a high bonding strength.

[0018] Another object of the present invention is to provide a cold-pressed polyester adhesive laminated paperboard for electrical use, wherein the shrinkage rate of the polyester adhesive used in the cold-pressed polyester adhesive laminated paperboard for electrical use is small, and the shrinkage rate of the insulating paperboard used in the cold-pressed polyester adhesive laminated paperboard for electrical use is close.

[0019] Another object of the present invention is to provide a cold-pressed polyester adhesive laminated paperboard for electrical use, wherein the polyester adhesive layer formed by the polyester adhesive used in the cold-pressed polyester adhesive laminated paperboard for electrical use has excellent mechanical properties.

[0020] Another object of the present invention is to provide a cold-pressed polyester adhesive laminated paperboard for electrical use, wherein the polyester adhesive used in the cold-pressed polyester adhesive laminated paperboard for electrical use has a large elastic modulus.

[0021] Another object of the present invention is to provide a cold-pressed polyester adhesive laminated paperboard for electrical use, wherein the cold-pressed polyester adhesive laminated paperboard for electrical use is used for transformer insulation end rings to avoid partial discharge, thereby greatly improving the reliability and service life of the power transformer.

[0022] According to one aspect of the present invention, the present invention provides a cold-pressed polyester adhesive electrical laminated paperboard, comprising a plurality of stacked insulating paperboards and a plurality of polyester adhesive layers, wherein a layer of the polyester adhesive layer is arranged between each two adjacent insulating paperboards, wherein each of the polyester adhesive layers is bonded together by a cold-pressing process to form two adjacent insulating paperboards, wherein the polyester adhesive layer comprises an adhesive layer, a first permeable structure and a second permeable structure, wherein the adhesive layer is formed between two adjacent insulating paperboards, wherein the first permeable structure extends from one side of the adhesive layer to the insulating paperboard on the side and penetrates into the insulating paperboard on the side by a first thickness, wherein the second permeable structure extends from the other side of the adhesive layer to the insulating paperboard on the other side and penetrates into the insulating paperboard on the other side by a second thickness.

[0023] According to one embodiment of the present invention, the polyester glue layer is formed between the insulating paperboards by cold pressing of polyester glue, wherein the polyester glue is mainly composed of unsaturated polyester resin, organic solvent and magnesium silicate mineral filler, wherein the molecular structure of the unsaturated polyester resin is as follows:

[0024]

[0025] According to one embodiment of the present invention, the first thickness and the second thickness are 1-2 mm, wherein the organic solvent is selected from formates and styrene, and the magnesium silicate mineral filler is sodium silicate.

[0026] According to an embodiment of the present invention, the mass proportion of the unsaturated polyester resin is 38-40%, the mass proportion of the organic solvent is 30-32%, and the mass proportion of the magnesium silicate mineral filler is 28-30%.

[0027] According to another aspect of the present invention, the present invention further provides a cold-pressed polyester adhesive electrical laminated paperboard. The cold-pressed polyester adhesive electrical laminated paperboard is made by the following steps:

[0028] A) drying;

[0029] B) gluing; and

[0030] C) cold pressing;

[0031] In step A, a plurality of insulating paperboards are dried by vacuum drying;

[0032] Wherein step B applies polyester glue to the insulating paperboard by means of glue coating;

[0033] In step C, the polyester glue coated on the insulating paperboard is cold-pressed between the insulating paperboards by using a press and a pressing plate at room temperature to form a polyester glue layer between each adjacent insulating paperboard.

[0034] According to one embodiment of the present invention, step C comprises the following steps:

[0035] C1) squeezing out excess polyester glue;

[0036] C2) the polyester glue penetrates into the insulating paperboard;

[0037] C3) pressurize to half of a preset pressure and maintain for 1 to 2 minutes; and

[0038] C4) pressurizing to the preset pressure and maintaining it for 2 hours.

[0039] According to one embodiment of the present invention, the preset pressure is 0.6 MPa.

[0040] According to one embodiment of the present invention, the gluing time in step B is less than 50 minutes.

[0041] According to an embodiment of the present invention, during the gluing process, the surface temperature of the insulating paperboard is kept consistent with its ambient temperature, wherein the ambient temperature is greater than 14°C.

[0042] According to one embodiment of the present invention, during the cold pressing process, the surface temperature of the insulating paperboard, the surface temperature of the press plate and the ambient temperature are kept consistent, wherein the ambient temperature is 18-25°C.

[0043] According to one embodiment of the present invention, the polyester glue is composed of unsaturated polyester resin, organic solvent and magnesium silicate mineral filler.

[0044] According to one embodiment of the present invention, the drying temperature is 100-110° C., the drying vacuum degree is 600 Pa, and the drying time is greater than 8 hours.

[0045] According to one embodiment of the present invention, the insulating paperboard after high-temperature vacuum drying is cooled to 14-28° C. within 4 hours after drying.

[0046] According to one embodiment of the present invention, the production of the cold-pressed polyester adhesive electrical laminated paperboard further comprises the following steps:

[0047] D) 24 hours of static storage; and

[0048] E) machining;

[0049] After machining, the cold-pressed polyester adhesive electrical laminated paperboard is used as an insulating end ring for a transformer. According to one embodiment of the present invention, the polyester adhesive is mainly composed of an unsaturated polyester resin, an organic solvent, and a magnesium silicate mineral filler, wherein the mass proportion of the unsaturated polyester resin is 38-40%, the mass proportion of the organic solvent is 30-32%, the mass proportion of the magnesium silicate mineral filler is 28-30%, the organic solvent is selected from formate and styrene, the magnesium silicate mineral filler is sodium silicate, and the molecular structure of the unsaturated polyester resin is as follows:

[0050] BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 The figure is a schematic diagram of the three-dimensional structure of a cold-pressed polyester adhesive electrical laminated paperboard according to a preferred embodiment of the present invention.

[0052] Figure 2 It is a cross-sectional enlarged structural schematic diagram of the cold-pressed polyester adhesive electrical laminated paperboard according to the above preferred embodiment of the present invention.

[0053] Figure 3 The figure is a schematic diagram of the manufacturing process of the cold-pressed polyester adhesive electrical laminated paperboard according to the above preferred embodiment of the present invention.

[0054] Figure 4 It is a flow chart of the method for making the cold-pressed polyester adhesive electrical laminated paperboard according to the above preferred embodiment of the present invention.

[0055] Figure 5 It is a schematic diagram of the drying process and drying conditions in the method for making the cold-pressed polyester adhesive electrical laminated paperboard according to the above preferred embodiment of the present invention.

[0056] Fig. 6A The structure of a polyester layer of the cold-pressed polyester adhesive electrical laminated paperboard according to the above preferred embodiment of the present invention is explained.

[0057] Figure 6B The phenolic resin glue layer structure of laminated paperboard according to the prior art is explained.

[0058] Figure 7 The performance parameters of the cold pressed polyester adhesive electrical laminated paperboard according to the above preferred embodiment of the present invention are explained. DETAILED DESCRIPTION

[0059] The following description is used to disclose the present invention so that those skilled in the art can implement the present invention. The preferred embodiments described below are only examples, and those skilled in the art can think of other obvious variations. The basic principles of the present invention defined in the following description can be applied to other embodiments, variations, improvements, equivalents, and other technical solutions that do not deviate from the spirit and scope of the present invention.

[0060] Those skilled in the art should understand that, in the disclosure of the present invention, the terms "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicating the orientation or position relationship are based on the orientation or position relationship shown in the drawings, which are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, the above terms should not be understood as limiting the present invention.

[0061] It is to be understood that the term "one" should be understood as "at least one" or "one or more", that is, in one embodiment, the number of an element may be one, while in another embodiment, the number of the element may be multiple, and the term "one" should not be understood as a limitation on the quantity.

[0062] Specification of the drawings Figure 1 and Figure 2 The structure of a cold-pressed polyester adhesive electrical laminated paperboard according to a preferred embodiment of the present invention is explained. The cold-pressed polyester adhesive electrical laminated paperboard 10 comprises multiple layers of insulating paperboard 11 and multiple polyester adhesive layers 12, wherein the multiple layers of insulating paperboard 11 are stacked together, wherein a layer of the polyester adhesive layer 12 is disposed between every two layers of insulating paperboard 11, so that the polyester adhesive layer 12 firmly connects the two layers of insulating paperboard 11 separated on both sides together. Specifically, a layer of polyester adhesive 102 is coated between every two layers of insulating paperboard 11, wherein under the action of a press and a press plate, the polyester adhesive 102 is combined and bonded with the insulating paperboard 11 on both sides, thereby forming the polyester adhesive layer 12 between adjacent insulating paperboards 11, and tightly bonding the adjacent insulating paperboards 11 together.

[0063] For the convenience of description, the structure of the cold-pressed polyester adhesive electrical laminated paperboard 10 is partially shown by taking two adjacent layers of insulating paperboard 11a, 11b and the polyester adhesive layer 12a therebetween as an example. Figure 2 A first insulating paperboard 11a and a second insulating paperboard 11b are arranged adjacent to each other, and a first polyester adhesive layer 12a is formed between the first insulating paperboard 11a and the second insulating paperboard 11b, and the first insulating paperboard 11a and the second insulating paperboard 11b are firmly bonded together. Specifically, referring to the drawings of the specification Figure 2The polyester adhesive layer 12a includes an adhesive layer 121a, a first permeable structure 122a and a second permeable structure 123a, wherein the adhesive layer 121a is formed between the first insulating paperboard 11a and the second insulating paperboard 11b, wherein the first permeable structure 122a extends from one side of the adhesive layer 121a to the first insulating paperboard 11a and penetrates into the first insulating paperboard 11a to a first thickness, wherein the second permeable structure 123a extends from the other side of the adhesive layer 121a to the second insulating paperboard 11b and penetrates into the second insulating paperboard 11b to a second thickness. Under the synergistic effect of the first permeable structure 122a, the second permeable structure 123a and the adhesive layer 121a, the first insulating paperboard 11a and the second insulating paperboard 11b are firmly bonded as a whole. According to the preferred embodiment of the present invention, the first thickness and the second thickness are 1-2 mm.

[0064] The polyester adhesive layer 12 is formed by a cold pressing process, wherein each of the polyester adhesive layers 12 formed by the cold pressing process comprises an adhesive layer 121, a first permeable structure 122 and a second permeable structure 123, wherein the adhesive layer 121 is formed between two adjacent insulating paperboards 11, wherein the first permeable structure 122 extends from one side of the adhesive layer 121 to the insulating paperboard 11 on that side and penetrates into the insulating paperboard 11 on that side, wherein the second permeable structure 123 extends from the other side of the adhesive layer 121 to the insulating paperboard 11 on the other side and penetrates into the insulating paperboard 11 on the other side. According to the preferred embodiment, the raw material of the insulating paperboard 11 is selected from t3 and t5 insulating paperboards, wherein the thickness of the first permeable structure 122 and the second permeable structure 123 is 1-2 mm. Under the synergistic effect of the first permeable structure 122, the second permeable structure 123 and the adhesive layer 121, adjacent insulating paperboards 11 are firmly bonded as a whole, and then the multiple insulating paperboards 11 stacked together are firmly bonded as a whole by the multiple polyester adhesive layers 12, thereby forming the cold-pressed polyester adhesive electrical laminated paperboard 10 with preset indicators such as thickness and strength.

[0065] Specifically, the performance parameters of the cold-pressed polyester adhesive electrical laminated paperboard 10 are as follows: Figure 7 shown.

[0066] Specification of the drawings Figure 3 The method for making the cold-pressed polyester adhesive electrical laminated paperboard 10 according to the preferred embodiment of the present invention is explained, comprising the following steps:

[0067] A) drying;

[0068] B) Gluing;

[0069] C) cold pressing;

[0070] D) static storage; and

[0071] E) Machining.

[0072] According to the preferred embodiment of the present invention, step A dries the insulating paperboard 11, wherein the drying conditions are as follows: drying temperature is 100-110°C, drying vacuum is 600Pa, and drying time is greater than 8h. Specifically, the insulating paperboard 11 is placed on a bracket and hung in a vacuum tank for drying. When the temperature in the vacuum tank reaches 105°C, vacuuming begins. When the vacuum reaches 600Pa, the temperature is maintained at 100-110°C. After drying for more than 8 hours, the vacuum is broken. Then, within 4 hours, the surface temperature of the insulating paperboard 11 is cooled to room temperature. Refer to the attached drawings of the specification. Figure 5 .

[0073] According to the preferred embodiment of the present invention, the insulating paperboard 11 is made of paperboard with specifications of t3, t4 or t5.

[0074] According to the preferred embodiment of the present invention, step B is to glue the insulating paperboard 11 by gluing. Specifically, step B is to apply polyester glue 102 to the insulating paperboard 11 at a preset ambient temperature. It is worth mentioning that during the gluing process, the surface temperature of the insulating paperboard 11 is consistent with the ambient temperature. During the cold pressing process, the surface temperature of the insulating paperboard 11 and the surface temperature of the press plate are consistent with the ambient temperature, wherein the ambient temperature is greater than or equal to 14°C, and preferably, the ambient temperature is 18-25°C.

[0075] It is worth mentioning that in order to avoid failure of the bonding operation due to the curing of the glue, the gluing process needs to be carried out quickly. According to this preferred embodiment of the present invention, the gluing time is less than 50 minutes, thereby reserving sufficient operation time for the cold pressing step C.

[0076] Step C uses a press and a pressing plate to press the polyester glue 102 onto the insulating paperboard 11 at room temperature. The whole process does not require heating, so it is called cold pressing. Specifically, after the press is raised, the insulating paperboard 11 coated with polyester glue 102 is driven to rise together. When the insulating paperboard 11 coated with polyester glue 102 lifts one or two pressing plates above, the press stops for 1 to 2 minutes to squeeze out the excess polyester glue 102 and allow the polyester glue 102 to fully penetrate the insulating paperboard 11. Then, the press continues to be raised and pressurized to half of a preset pressure. After maintaining the pressure for 1 to 2 minutes, the pressure continues to be increased to the preset pressure of 0.6 MPa. The press continues to maintain the pressure for 2 hours. Step C needs to complete the step of pressurizing to the preset pressure of 0.7 MPa before the polyester glue 102 solidifies, so as to fully ensure the cold pressing effect.

[0077] Specifically, step C includes the following steps:

[0078] C1) squeeze out excess polyester glue;

[0079] C2) Polyester glue penetrates into the insulation paperboard;

[0080] C3) pressurize to half of the preset pressure and maintain for 1 to 2 minutes; and

[0081] C4) pressurize to the preset pressure and maintain for 2 hours.

[0082] Step D: After the laminate obtained in step C is taken out from the press, it is left to stand for 24 hours.

[0083] After the above four steps, the obtained cold-pressed polyester adhesive electrical laminated paperboard 10 can be further subjected to mechanical processing in step E, so as to have a preset shape and size, and thus can be used as an insulating paperboard for a transformer.

[0084] It is worth mentioning that according to the preferred embodiment of the present invention, the cold-pressed polyester adhesive electrical laminated paperboard 10 manufactured by cold-pressing process using polyester resin adhesive has excellent performance.

[0085] The applicant compared the performance of the cold-pressed polyester adhesive electrical laminated paperboard 10 with that of hot-pressed 1411 phenolic resin laminated paperboard, hot-pressed double-sided adhesive paper laminated paperboard, cold-pressed water-based casein adhesive laminated paperboard, cold-pressed dextrin starch laminated paperboard, hot-pressed PVA polyvinyl alcohol laminated paperboard, hot-pressed GX-1 laminated paperboard, and cold-pressed woodworking adhesive polyvinyl acetate laminated paperboard. The comparison results show that compared with laminated paperboards made with other adhesives and other processes, the cold-pressed polyester adhesive electrical laminated paperboard 10 has excellent performance in terms of bending strength, bonding strength, electrical properties, etc.

[0086] According to this preferred embodiment of the present invention, the main components of the polyester glue 102 are unsaturated polyester resin, organic solvent and magnesium silicate mineral filler, wherein the mass proportion of the unsaturated polyester resin is 38-40%, the mass proportion of the organic solvent is 30-32%, and the mass proportion of the magnesium silicate mineral filler is 28-30%.

[0087] According to this preferred embodiment of the present invention, the organic solvent is selected from formates and styrene; wherein the magnesium silicate mineral filler is specifically implemented as sodium silicate.

[0088] The unsaturated polyester resin is selected from polyester resins with a molecular weight of about 3000 (e.g., a molecular weight of 2500-3500), so as to ensure its wettability to the insulating paperboard 11 and avoid excessive fluidity and flow. In addition, the tanδ value of the cured polyester resin is 0.4×10 -2 ~0.6×10 -2, requiring the polyester resin to have a small dipole moment, a small polarizability, and good dielectric properties. When the unsaturated polyester resin has a functionality of 3 or more, it has a spatial network structure during the reaction, and its polymer is not easy to soften or deform after heating, and it can neither dissolve nor melt, and has good thermosetting properties.

[0089] According to this preferred embodiment of the present invention, the molecular structure diagram of the unsaturated polyester resin is as follows:

[0090]

[0091] The unsaturated polyester resin with the above molecular structure has many excellent properties, so it is suitable for use as an important raw material for cold-pressed polyester adhesive electrical laminated paperboard. First, the double bonds at both ends of the molecular chain of the unsaturated polyester resin are extremely active, so that the polyester adhesive can be quickly cured under cold-pressing conditions and quickly reach the use strength, thereby obtaining a polymer with a preset high strength. Secondly, the unsaturated polyester resin has more secondary hydroxyl groups, which can improve the wettability and adhesion of the insulating paperboard 11, and thus help to improve the mechanical strength of the cold-pressed polyester adhesive electrical laminated paperboard. Third, the unsaturated polyester resin is cross-linked only at both ends of the molecule during polymerization, and the molecular chain can be elongated under stress to absorb external force and thermal shock to improve the resistance to microcracks or cracking. Fourth, the unsaturated polyester resin has toughness and a small volume shrinkage after curing, so that the internal stress after lamination, such as cold pressing, can be eliminated.

[0092] Compared with the phenolic resin adhesive layer used in the conventional voltage-changing laminated paperboard, the polyester adhesive used in the polyester adhesive type electrical laminated paperboard using the polyester adhesive can penetrate the insulating paperboard 11 more deeply, thereby providing the polyester adhesive electrical laminated paperboard with better mechanical properties after curing. 6A of the accompanying drawings of the specification illustrates the structure of the polyester adhesive layer 12 of the polyester adhesive type electrical laminated paperboard according to the preferred embodiment of the present invention. Figure 6B The structure of the traditional phenolic resin adhesive layer is explained. Figure 6B As shown, the thickness of the phenolic resin layer is only about 0.2-0.4 mm. It can be seen that the penetration depth of the polyester adhesive layer 12 in the insulating paperboard 11 is much greater than that of the conventional phenolic resin adhesive layer. In addition, due to the strong adhesiveness of the polyester adhesive, the mechanical strength of the cold-pressed polyester adhesive electrical laminated paperboard is far superior to that of the prior art.

[0093] Specifically, the cold-pressed polyester adhesive electrical laminated paperboard uses a polyester resin with excellent permeability, and the thickness of the adhesive layer on the joint surface between the single board layers, that is, the thickness of the first permeable structure 122 and the second permeable structure 123 can reach 2mm. Compared with the phenolic resin commonly used at present, the thickness of the adhesive layer on the joint surface between the single board layers is only about 0.2-0.4mm. The cold-pressed polyester adhesive with excellent permeability passes through the surface of the insulating paperboard 11 with a layered structure, and like a rivet, the single board is tightly bonded together through the riveting action, avoiding the problem of interlayer cracking that is easy to occur when the existing insulating adhesive is used to bond the paperboard. At the same time, through good permeability and the filtering effect of the paperboard fibers of the insulating paperboard 11, various fine bubbles that may exist in the glue are eliminated, ensuring that the adhesive layer is tight and free of bubbles, laying a good foundation for electrical performance.

[0094] It is worth mentioning that the cold-pressed polyester adhesive electrical laminated paperboard 10 can have a preset shape and size after mechanical processing, and can be used as an insulating end ring for a transformer.

[0095] It is worth mentioning that according to the preferred embodiment of the present invention, the cold pressed polyester adhesive electrical laminated paperboard 10 is formed and then mechanically processed to obtain the transformer insulating end ring with a preset shape and size. Before the drying step, there is a step a of preparing materials.

[0096] Step a: according to the shape and size of the transformer insulation end ring to be processed, a processing allowance is reserved and the insulation paperboard is sawed to ensure that the cold-pressed polyester adhesive electrical laminated paperboard 10 obtained after cold pressing is suitable for further mechanical processing to obtain the required transformer insulation end ring.

[0097] It is worth mentioning that after sawing the insulating cardboard, the chips on the surface of the sawn insulating cardboard need to be cleaned and excess burrs need to be removed to prevent chips or burrs from mixing into the polyester glue during the gluing process, which will be difficult to remove and affect product quality.

[0098] The drying step of step A is a very critical preparation step. Step A dries the insulating paperboard by vacuum drying, thereby preventing the laminated paperboard from cracking after bonding. It is worth mentioning that multiple insulating paperboards keep a distance and do not touch each other during the drying process, thereby ensuring that the insulating paperboard as a whole can be heated sufficiently and evenly. According to this preferred embodiment of the present invention, during the drying process, the insulating paperboards are separated by 5-10 mm pads.

[0099] According to the preferred embodiment of the present invention, in step A, the insulating paperboard is dried by high-temperature vacuum drying. After the drying is completed, the vacuum is released and the paperboard is cooled.

[0100] According to an alternative implementation of this preferred embodiment of the present invention, the insulating paperboard 11 can also be dried by hot air circulation, for example, by hot air circulation drying at 105° C. for more than 16 hours.

[0101] According to this preferred embodiment of the present invention, the insulating paperboard after baking is immediately cooled by auxiliary cooling, for example, fan cooling, so that the surface temperature of the insulating paperboard is cooled to room temperature within 3 hours, wherein the room temperature is maintained at 14-28°C, preferably, the room temperature is maintained at 18-25°C.

[0102] After the drying step and before the gluing step, a process of cleaning foreign matter and removing excess burrs is performed to fully ensure that the product quality will not be affected by foreign matter mixed into the polyester glue during the gluing process and difficult to remove.

[0103] It should be noted that in the apparatus and method of the present application, the components or steps in different embodiments can be decomposed and / or recombined without departing from the principles of the present invention. Such decomposition and / or recombination should be considered to be included in the inventive concept of the present application.

[0104] It should be understood by those skilled in the art that the embodiments of the present invention described above and shown in the accompanying drawings are only examples and do not limit the present invention. The purpose of the present invention has been fully and effectively achieved. The functional and structural principles of the present invention have been demonstrated and explained in the embodiments, and the embodiments of the present invention may be deformed or modified in any way without departing from the principles.

Claims

1. A cold pressed polyester adhesive electrical laminated paperboard, characterized in that: The invention comprises a plurality of stacked insulating paperboards and a plurality of polyester adhesive layers, wherein a layer of the polyester adhesive layer is arranged between each two adjacent insulating paperboards, wherein each of the polyester adhesive layers is used to bond two adjacent insulating paperboards together by a cold pressing process, wherein the polyester adhesive layer comprises an adhesive layer, a first permeable structure and a second permeable structure, wherein the adhesive layer is formed between two adjacent insulating paperboards, wherein the first permeable structure extends from one side of the adhesive layer to the insulating paperboard on the side and penetrates into the insulating paperboard on the side by a first thickness, wherein the second permeable structure extends from the other side of the adhesive layer to the insulating paperboard on the other side and penetrates into the insulating paperboard on the other side by a second thickness; The polyester glue layer is formed between the insulating paperboards by cold pressing of polyester glue, wherein the polyester glue is mainly composed of unsaturated polyester resin, organic solvent and magnesium silicate mineral filler, wherein the molecular structure of the unsaturated polyester resin is as follows:

2. The cold-pressed polyester adhesive electrical laminated paperboard according to claim 1, wherein the first thickness and the second thickness are 1-2 mm, wherein the organic solvent is selected from formates and styrene, and wherein the magnesium silicate mineral filler is sodium silicate.

3. The cold-pressed polyester adhesive electrical laminated paperboard according to claim 2, wherein the mass proportion of the unsaturated polyester resin is 38-40%, the mass proportion of the organic solvent is 30-32%, and the mass proportion of the magnesium silicate mineral filler is 28-30%.

4. A cold pressed polyester adhesive electrical laminated paperboard, characterized in that: Made by following the steps below: A) drying; B) gluing; and C) cold pressing; In step A, a plurality of insulating paperboards are dried by vacuum drying; Wherein step B applies polyester glue to the insulating paperboard by means of glue coating; In step C, the polyester glue coated on the insulating paperboard is cold-pressed between the insulating paperboards by using a press and a pressing plate at room temperature to form a polyester glue layer between each adjacent insulating paperboard; The polyester glue is mainly composed of unsaturated polyester resin, organic solvent and magnesium silicate mineral filler, wherein the mass proportion of the unsaturated polyester resin is 38-40%, the mass proportion of the organic solvent is 30-32%, the mass proportion of the magnesium silicate mineral filler is 28-30%, the organic solvent is selected from formate and styrene, the magnesium silicate mineral filler is sodium silicate, and the molecular structure of the unsaturated polyester resin is as follows:

5. The cold-pressed polyester adhesive electrical laminated paperboard according to claim 4, wherein step C comprises the following steps: C1) squeezing out excess polyester glue; C2) the polyester glue penetrates into the insulating paperboard; C3) pressurize to half of a preset pressure and maintain for 1 to 2 minutes; and C4) pressurizing to the preset pressure and maintaining it for 2 hours.

6. The cold-pressed polyester adhesive electrical laminated paperboard according to claim 5, wherein the preset pressure is 0.6 MPa.

7. The cold-pressed polyester adhesive electrical laminated paperboard according to claim 6, wherein the gluing time in step B is less than 50 minutes.

8. The cold-pressed polyester adhesive electrical laminated paperboard according to claim 7, wherein during the gluing process, the surface temperature of the insulating paperboard is kept consistent with its ambient temperature, wherein the ambient temperature is greater than 14°C.

9. The cold-pressed polyester adhesive electrical laminated paperboard according to claim 8, wherein during the cold pressing process, the surface temperature of the insulating paperboard, the surface temperature of the press plate and the ambient temperature remain consistent, wherein the ambient temperature is 18-25°C.

10. The cold-pressed polyester adhesive electrical laminated paperboard according to claim 9, wherein the polyester adhesive is composed of unsaturated polyester resin, organic solvent and magnesium silicate mineral filler.

11. The cold-pressed polyester adhesive electrical laminated paperboard according to claim 10, wherein the drying temperature is 100-120°C, the drying vacuum degree is 600 Pa, and the drying time is greater than 8 hours.

12. The cold-pressed polyester adhesive electrical laminated paperboard according to claim 11, wherein the insulating paperboard after high-temperature vacuum drying is cooled to 14-28°C within 4 hours after being baked.

13. The cold-pressed polyester adhesive electrical laminated paperboard according to claim 12, wherein the preparation of the cold-pressed polyester adhesive electrical laminated paperboard further comprises the following steps: D) 24 hours of static storage; and E) machining; After being machined, the cold-pressed polyester adhesive electrical laminated paperboard is used as an insulating end ring for a transformer.

Images